The invention relates to a gear pump for feeding of fluids, in which the pump includes gears arranged axially parallel to each other and meshing in pairs within a housing having a peripheral wall. One gear is axially fixed to the housing while the other is movable in the axial direction.
Gear pumps of this type are employed for stationary as well as for mobil applications. The known advantages mainly consist in the fact that high and super high pressures may be achieved, thereby allowing for relatively exact volumetric metering.
It has become known in the relevant art to shift gears which are meshing with each other, in an axial direction relative to each other, in order to change the amount of pumped fluid during operation. This concept is disclosed in U.S. Pat. No. 5,184,947 wherein a gear which is axially non-shiftable is journalled in a housing. A second gear which meshes with the first gear, is supported by a slide block, which is shiftable relative to the axis of the first gear.
German Patent No. OS-41 21 074 A1 describes an external gear pump for a continuously variable flow of fluid. This patent discloses two gears which are shiftable relative to each other. The driven gear is journalled in a housing, whereas the idle gear may be shifted depending on the pressure differential of the fluid at the pump.
It is the disadvantage of all these known devices that the sealing of the pumping chamber is not satisfactory. The sealing devices are subject to very substantial pressures and therefore to a high wear which limits the lifetime of the gear pump.